Heat exchanger, fluorination method of heat exchanger or its components and manufacturing method of heat exchanger

ABSTRACT

The heat exchanger according to the present invention includes a heat exchanger component in which a fluoride layer  10  is formed at the surface layer portion. It is preferable that the fluoride layer  10  falls within the range of from 2 nm to 10 μm in thickness. It is preferable that the component is at least one of a fin and a plate. Furthermore, it is preferable that the fluoride layer  10  is formed on a substrate via an intermediate layer  2.  It is preferable that the intermediate layer  2  includes an anodized oxide layer  3  and/or a nickel plated layer  4.  The heat exchanger is excellent in corrosion resistance against water, vapor and the like The heat exchanger is preferably used, especially, for a fuel cell.

[0001] Priority is claimed to Japanese Patent Application No.2001-328184, filed on Oct. 25, 2001 and U.S. Provisional PatentApplication No. 60/341,249, filed on Dec. 20, 2001, the disclosure ofwhich are incorporated by reference in their entireties.

CROSS REFERENCE TO RELATED APPLICATIONS

[0002] This application is an application filed under 35 U.S.C. §111 (a)claiming the benefit pursuant to 35 U.S.C. §119(e) (1) of the filingdate of U.S. Provisional Application No. 60/341, 249 filed on Dec. 20,2001 pursuant to 35 U.S.C. §111(b).

FIELD OF THE INVENTION

[0003] The present invention relates to a heat exchanger to be used as,for example, an evaporator, a condenser, a radiator or an oil cooler, amethod of fluorinating a heat exchanger or its components and a methodof manufacturing a heat exchanger. More specifically, the presentinvention relates to a heat exchanger preferably used as a heatexchanger using water (especially, hot water of room temperature to 100°C. or hot water containing long-life coolant of 80 to 150° C.) as heatmedium, a heat exchanger preferably used especially for a heat exchangerunder a water environment, a vapor environment, a fuel cell gasenvironment or the like, a method of fluorinating a heat exchanger orits components and a method of manufacturing a heat exchanger.

BACKGROUND ART

[0004] Metallic materials have been used as materials of heat exchangersfor automobiles, etc. from a long time ago because it generally hascharacteristics such as an easy-to-work characteristic and high thermalconductivity. Due to its insufficient corrosion resistance, however,various cases in which heat exchangers lost their function due to thecorrosion from the surface thereof that caused penetration in sort timewere reported.

[0005] As the countermeasures thereof, various anti-corrosionprocessings are conventionally conducted to a heat exchanger or thesurfaces of the components. For example, a formation of chemicalconversion coating on a surface of a heat exchanger or its componentswas performed as corrosion resistance processing.

[0006] Furthermore, recently, in order to improve the corrosionresistance, various improvements are made to the aforementionedcorrosion resistance processing. For example, according to JapanesePatent No. 2,076,381 (Japanese Examined Laid-open Patent Publication No.H7-109355 and U.S. Pat. No. 4,726,886), in a fin-tube type heatexchanger, after conducting chemical conversion treatment on thesurfaces of the fins and the tubes, the treated fins and tubes areimmersed in a mixed water solution of polyvinyl pyrrolidone andpotassium silicate, thereby improving the corrosion resistance (seePatent Document No. 1).

[0007] Patent Document No. 1

[0008] Japanese Examined Laid-open Patent Application No. 7-109355

[0009] (see pages 2-5, FIG. 6)

[0010] (U.S. Pat. No. 4,726,886)

[0011] However, according to the aforementioned corrosion resistanceprocessing method, a metallic oxide layer is formed on a surface of abeat exchanger or its components. However, since the metallic oxidelayer is poor against water, especially hot water of a room temperatureto 100° C., the conventional corrosion resistance processing method waspoor in reliability against water.

[0012] Especially, in recent years, in a heat exchanger for a fuel cell,it has been desired that a corrosion resistance processing methodexcellent in reliability against water, vapor and a fuel gas of a fuelcell is developed.

[0013] The present invention was made in view of the aforementionedtechnical background, and aims to provide a heat exchanger excellent incorrosion resistance, a method of fluorinating a heat exchanger or itscomponents and a method of manufacturing a heat exchanger.

[0014] Another object of the present invention will be apparent from thefollowing detailed embodiments of the present invention.

DISCLOSURE OF THE INVENTION

[0015] The present invention provides the following means:

[0016] (1) A heat exchanger including a heat exchanger component havinga surface layer portion in which a fluoride layer is formed.

[0017] (2) The heat exchanger as recited iii the aforementioned item(1), wherein a thickness of the fluoride layer falls within the range offrom 2 nm to 10 μm.

[0018] (3) The heat exchanger as recited in the aforementioned item (1),wherein the heat exchanger is a fin-plate type heat exchanger, andwherein the component is at least one of a fin and a plate.

[0019] (4) The heat exchanger as recited in the aforementioned item (1),wherein the heat exchanger uses water as beat medium.

[0020] (5) The heat exchanger as recited in the aforementioned item (1),wherein the heat exchanger is used under a water environment, a vaporenvironment, or a fuel gas environment of a fuel cell.

[0021] (6) The heat exchanger as recited in the aforementioned item (1),wherein a layer containing catalyst is formed on a surface of thefluoride layer.

[0022] (7) The heat exchanger as recited in the aforementioned item (1),wherein the heat exchanger is for use in a fuel cell.

[0023] (8) The heat exchanger as recited in the aforementioned item (1),wherein the heat exchanger is a fin-plate type heat exchanger for a fuelcell to be used under a fuel gas environment of a fuel cell, and whereina layer containing catalyst for accelerating a reaction of carbonmonoxide included in the fuel gas and oxygen.

[0024] (9) The heat exchanger as recited in the aforementioned item (1),wherein a substrate of the component is substantially made of aluminumor its alloy.

[0025] (10) The heat exchanger as recited in the aforementioned item(1), wherein the fluoride layer is formed on a surface of the substrateof the component.

[0026] (11) The heat exchanger as recited in the aforementioned item(10), wherein the fluoride layer is substantially made of fluoridegenerated by performing fluorination processing of the surface of thesubstrate.

[0027] (12) The heat exchanger as recited in the aforementioned item(1), wherein the fluoride layer is formed on a surface of anintermediate layer formed on a surface of the substrate of thecomponent.

[0028] (13) The heat exchanger as recited in the aforementioned item(12), wherein the fluoride layer is substantially made of fluoridegenerated by performing fluorination processing of the surface of theintermediate layer.

[0029] (14) The heat exchanger as recited in the aforementioned item(12) or (13), wherein the intermediate layer includes a layer which issubstantially made of oxide generated by performing forcible oxidationof the surface of the substrate.

[0030] (15) The heat exchanger as recited in aforementioned item (12) or(13), wherein the intermediate layer includes an anodized oxide layerformed by anodizing the surface of the substrate.

[0031] (16) The heat exchanger as recited in the aforementioned item(1), wherein the fluoride layer is formed on a surface of an anodizedoxide layer formed by anodizing a surface of a substrate of thecomponent and substantially made of fluoride generated by performingfluorination processing of the surface of the anodized oxide layer.

[0032] (17) The heat exchanger as recited in the aforementioned item(1), wherein the fluoride layer is formed on a surface of a plated layercontaining nickel formed on a surface of a substrate of the componentand substantially made of fluoride generated by performing fluorinationprocessing of the surface of the plated layer.

[0033] (18) The heat exchanger as recited in the aforementioned item(17), wherein the plated layer is substantially made of an electrolessnickel plating.

[0034] (19) The heat exchanger as recited in the aforementioned item(17), wherein the plated layer is substantially made of electrolessnickel-phosphorus alloy plating.

[0035] (20) The heat exchanger as recited in the aforementioned item(1), wherein the fluoride layer is formed on a surface of the platedlayer constituting an intermediate layer including an anodized oxidelayer formed by anodizing the surface of the substrate of the componentand the plated layer formed on a surface of the anodized oxide layer andcontaining nickel, and substantially made of fluoride generated byperforming fluorination processing of the surface of the plated layer.

[0036] (21) The heat exchanger as recited in the aforementioned item(20), wherein the plated layer is substantially made of electrolessnickel plating.

[0037] (22) The heat exchanger as recited in the aforementioned item(20), wherein the plated layer is substantially made of electrolessnickel-phosphorus alloy plating.

[0038] (23) A method of fluorinating a heat exchanger or its component,comprising;

[0039] heating a heat exchanger or its component in an atmospherecontaining a fluorination processing gas to thereby form a fluoridelayer in a surface layer portion of the heat exchanger or its component.

[0040] (24) The method of fluorinating a heat exchanger or its componentas recited in the aforementioned item (23), wherein the fluorinationprocessing gas is at least one gas selected from the group consisting ofa fluorine gas, a chlorine trifluoride gas and a nitrogen fluoride gas,wherein an inert gas is used as a base gas of the atmosphere, andwherein concentration of the fluorine gas or that of the fluoride gas isset so as to fall within the range of from 5 to 80 mass %.

[0041] (25) The method of fluorinating a heat exchanger or its componentas recited in the aforementioned item (24), wherein the concentration ofthe fluorine gas or that of the fluoride gas is set so as to fall withinthe range of from 10 to 60 mass %.

[0042] (26) The method of fluorinating a heat exchanger or its componentas recited in the aforementioned item (23), wherein the heating isperformed under heat processing conditions that a holding temperature is100° C. or more and a holding time is 5 hours or more.

[0043] (27) A method of fluorinating a heat exchanger or its component,comprising:

[0044] implanting an ionized fluorine into at least a part of a surfaceof a heat exchanger or its component to thereby form a fluoride layer ona surface layer portion of the heat exchanger or its component.

[0045] (28) A method of manufacturing a heat exchanger, comprising:

[0046] a heating step for heating a heat exchanger component in anatmosphere containing a fluorination processing gas; and

[0047] a fixing step for fixing the component processed by the heatingstep to a predetermined position of the heat exchanger.

[0048] (29) The method of manufacturing a heat exchanger as recited inthe aforementioned item (28), further comprising a catalyst containinglayer forming step for forming a layer containing catalyst on a surfaceof the component processed by the heating step.

[0049] (30) A method of manufacturing a heat exchanger, comprising:

[0050] a fluorine implanting step for implanting an ionized fluorineinto at least a part of a surface of a heat exchanger component; and

[0051] a fixing step for fixing the component processed by the fluorineimplanting step to a predetermined position of the heat exchanger.

[0052] (31) The method of manufacturing a heat exchanger according tothe aforementioned item (30), further comprising a catalyst containinglayer forming step for forming a layer containing catalyst on a portionof the surface of the component processed by the fluorine implantingstep to which the fluorine is implanted.

[0053] (32) A method of manufacturing a heat exchanger, comprising:

[0054] a heating step for heating a heat exchanger assembly in anatmosphere containing a fluorination processing gas, wherein the heatexchanger assembly is formed by assembling a plurality of heat exchangercomponents and integrally brazing the plurality of heat exchangercomponents in an assembled state.

[0055] (33) The method of manufacturing a heat exchanger as recited inthe aforementioned item (32), further comprising a catalyst containinglayer forming step for forming a layer containing catalyst on a surfaceof the assembly processed by the heating step.

[0056] (34) A method of manufacturing a heat exchanger, comprising:

[0057] a fluorine implanting step for implanting an ionized fluorineinto at least a part of a surface of a heat exchanger assembly, whereinthe heat exchanger assembly is formed by assembling a plurality of heatexchanger components and integrally brazing the plurality of heatexchanger components in an assembled state.

[0058] (35) The method of manufacturing a heat exchanger as recited inthe aforementioned item (34), further comprising a catalyst containinglayer forming step for forming a layer containing catalyst on a portionof the surface of the assembly processed by the fluorine implanting stepto which the fluorine is implanted.

[0059] Next, each of the above inventions will be explained.

[0060] According to the aforementioned invention (1), since a fluorideis generally low in thermodynamic free energy and the fluoride layer isformed on the surface layer portion of the heat exchanger component, thecomponent can have a layer thermodynamically stable on the surface layerportion and therefore becomes excellent in corrosion resistance.Furthermore, the adhesion to the layer containing the catalyst(hereinafter referred to as “catalyst containing layer”) which will bementioned later is improved. This prevents an exfoliation of thecatalyst containing layer assuredly.

[0061] In the present invention, the “fluoride layer” means a layerwhich is substantially made of fluoride. Furthermore, in the presentinvention, the “surface layer portion” of the component on which thefluoride layer is formed includes the surface of the component.Furthermore, as the component, a metallic component can be exemplified.

[0062] According to the aforementioned invention (2), the reason why thethickness of the fluoride layer is set to fall within the range of from2 nm to 10 μm is as follows. That is, it the thickness of the fluoridelayer is less than 2 nm, it cannot function as a corrosion processedlayer against water (especially against hot water). As a result,corrosion occurs in a relatively short time period. On the other hand,if the thickness of the fluoride layer exceeds 10 μm, although it mayfunction enough against a corrosion processed layer against water(especially against hot water), it takes a considerable time to form thefluoride layer. As a result, the cost for manufacturing the heatexchanger increases. Accordingly, it is preferable that the thickness ofthe fluoride layer falls within the range of from 2 nm to 10 μm. It ismore preferable that the thickness of the fluoride layer falls withinthe range of from 20 nm to 3 μm.

[0063] The thickness of the fluoride layer can be measured by variousmethods. For example, the thickness can be easily measured by a depthprofile measurement method using an XPS (X-ray PhotoelectronSpectroscopy).

[0064] According to the aforementioned invention (3), generally, thefins (especially outer fins) and plates among the various componentsconstituting a fin-plate type heat exchanger are components which arerequired to be excellent in corrosion resistance. Accordingly, it ispreferable that the component to which a fluoride layer is formed is atleast one of the fin (especially outer fins) and the plate.

[0065] According to the aforementioned invention (4), as the heatmedium, especially, water (including steam), hot water of a roomtemperature to 100° C. or a long-life coolant of 80 to 150° C., ispreferably used.

[0066] According to the aforementioned invention (5), the heat exchangercan demonstrate the extremely excellent corrosion resistance when it isused under a water environment, a vapor environment or a fuel gasenvironment of a fuel cell. As a fuel gas of a fuel cell, a hydrogen(H₂) gas is mainly used, and the combustion gas includes carbon monoxide(CO) gas, gasoline, alcohol (e.g., methanol), combustion gas, vapor,etc., as impurities. As a heat exchanger to be used under a fuel gasenvironment of a fuel gas, especially, a plate-fin type heat exchangeris preferably used. On the other hand, the fin-tube type heat exchangercan be used as a heat exchanger as a heater core.

[0067] According to the aforementioned present invention (6), the layercontaining catalyst (i.e., catalyst containing layer) may be a layeressentially made of catalyst, or a layer containing catalyst andsubstances other than catalyst. As the catalyst, a modified catalyst ofa fuel cell can be exemplified. Especially, it is preferable that thecatalyst is CO selective-oxidation reaction catalyst of a CO eliminationdevice of a fuel cell. As this CO selective-oxidation reaction catalyst,catalyst for accelerating the reaction of carbon monoxide (CO) containedin a fuel gas of a fuel cell and oxygen (O₂) (the reaction formula:CO+(½)O₂→CO₂) can be exemplified. By the function of this catalyst, thereaction of the carbon monoxide (CO) and the oxygen (O₂) is accelerated,and therefore carbon dioxide (CO₂) generates efficiently. This increasesthe purity of the hydrogen (H₂) gas as a fuel gas. Although Cu—Zn seriescatalyst and zeolitic series catalyst can be exemplified as the COselective-oxidation reaction catalyst, the catalyst is not limited tothe above in the present invention.

[0068] According to the aforementioned invention (7), a heat exchangerexcellent in corrosion resistance for a fuel cell can be provided.

[0069] According to the aforementioned invention (8), it is possible toprovide a fin-plate type heat exchanger for a fuel cell excellent incorrosion resistance and capable of efficiently eliminating carbonmonoxide (CO) contained in a fuel gas of a fuel cell.

[0070] In the heat exchanger for a fuel cell, the reasons why carbonmonoxide (CO) should be eliminated from the combustion gas of the fuelcell are as follows. That is, if the carbon monoxide (CO) contained inthe fuel gas of the fuel cell as an impurity is fed into the fuel cell,there are such possibilities that the performance of the fuel cell maydeteriorate and that the carbon monoxide (CO) may be discharged into theatmospheric air as a harmful gas as it is. In order to eliminate thecarbon monoxide (CO) from the fuel gas, the catalyst containing layer isformed on the surface of the fluoride layer. Furthermore, according tothe heat exchanger for a fuel cell, it is possible to set thetemperature of the fuel gas to the temperature at which the catalyst candemonstrate the function efficiently.

[0071] According to the aforementioned invention (9), since thesubstrate of the component is substantially made of aluminum or itsalloy, the heat conductivity becomes high and the heat exchangeperformance of the aforementioned heat exchanger improves. Furthermore,the heat exchanger becomes light in weight.

[0072] According to the aforementioned invention (11), in cases wherethe substrate of the components is substantially made of metal, thefluoride layer is substantially made of the fluoride of the metal.Concretely, in cases where the substrate of the component issubstantially made of, for example, aluminum or its alloy, the fluoridelayer is substantially made of aluminum fluoride or aluminum alloyfluoride.

[0073] According to the aforementioned invention (14), the layer whichis substantially made of fluoride generated by performing forcibleoxidation of the surface of the substrate is generally excellent incorrosion resistance. Accordingly, since the intermediate layer includessuch a layer, the corrosion resistance is further improved. As theforcible oxidation processing, anodizing processing which will beexplained later can be exemplified.

[0074] According to the aforementioned invention (15), since theanodized oxide layer is stable physically and chemically and theintermediate layer includes the anodized oxide layer, the corrosionresistance is further improved. The anodized oxide layer can be formedby various known anodizing processing, and the forming method is notlimited in the present invention. For example, an anodized oxide layercan be formed on a surface of a component by subjecting a substrate ofthe component immersed in an electrolytic bath containing apredetermined acid such as sulfuric acid, oxalic acid, chromic acid orthese mixed acids to anodizing processing. If necessary, the anodizedoxide layer may be subjected to sealing processing.

[0075] According to the aforementioned invention (16), since thefluoride layer is substantially made of fluoride generated by performingfluorination processing of the surface of the anodized oxide layer, thecorrosion resistance can be further improved.

[0076] According to the aforementioned invention (17), since a platedlayer containing nickel is generally excellent in corrosion resistanceand the fluoride layer is substantially made of fluoride generated byperforming -fluorination processing of the surface of the plated layer,the corrosion resistance can be further improved. The terminology“plated layer containing nickel” is used to mean the “layer containingnickel as a component element” and exclude the “layer containing nickelas an impurity element”. In this case, the fluoride layer issubstantially made of the compound of the structure element of theplated layer and fluorine. The plated layer is formed by, for example,an electrolytic plating method or an electroless plating method. As theplated layer, a nickel plated layer, a nickel-phosphorus alloy platedlayer, a nickel-tungsten alloy plated layer, anickel-phosphorus-tungsten alloy plated layer, a nickel-boron alloyplated layer, a nickel-phosphorus-boron alloy plated layer and anickel-copper alloy plated layer can be exemplified.

[0077] According to the aforementioned invention (18), since the platedlayer is substantially made of electroless nickel plating, the corrosionresistance can be assuredly improved.

[0078] According to the aforementioned invention (19), since the platedlayer is substantially made of electroless nickel-phosphorus alloyplating, the corrosion resistance can be assuredly improved

[0079] According to the aforementioned invention (20), the corrosionresistance can be further improved. In this case, the fluoride layer issubstantially made of, for example, the compound of the componentelement of the plated layer and fluorine. More specifically, thefluoride layer is made of, for example, nickel fluoride ornickel-phosphorus alloy fluoride.

[0080] According to the aforementioned invention (21), since the platedlayer is substantially made of electroless nickel plating, the corrosionresistance can be assuredly improved.

[0081] According to the aforementioned invention (22), since the platedlayer is substantially made of electroless nickel-phosphorus alloyplating, the corrosion resistance can be assuredly improved.

[0082] According to the aforementioned invention (23), the fluoridelayer can be easily formed on the surface layer portion of the heatexchanger or its component. As the fluorination processing gas, afluorine (F₂) gas or a fluoride gas (e.g., a nitrogen trifluoride (ClF₃)gas, a fluorination nitrogen (NF₃) gas) are preferably used.Furthermore, as the heating means, although various heating furnaces canbe used, especially an atmospheric heating furnace is preferably used.In the fluorination method according to the invention, a heat exchangeror its component is disposed in an atmospheric heating furnace, and agas containing a fluorination processing gas is supplied to the furnace.Then, the heat exchanger or its component is heated in the atmosphereunder predetermined heating processing conditions. By this, the surfaceof the heat exchanger or its component reacts to the fluorinationprocessing gas to thereby form a fluoride layer at the surface layerportion (including the surface) of the heat exchanger or its alloy.

[0083] According to the aforementioned invention (24), the reasons whythe concentration of the fluorine gas or that of the fluoride gas is netso as to fall within the range of from 5 to 80 mass % are as follows.That is, it the concentration is less than 5 mass %, the fluoride layerbecomes thin, which becomes difficult to obtain desired corrosionresistance. On the other hand, the more the concentration increases, themore the formation rate of the fluoride layer increases. However, if theconcentration exceed 80 mass %, the formation rate of the fluoride layerdoes not increase so much and will be saturated. Thus, the increase ofthe concentration becomes meaningless, and that the manufacturing costincreases. Accordingly, it is preferable that the concentration fallswithin the range of from 5 to 80 mass %. Especially, it is morepreferable that the concentration falls within the range of from 10 to60 mass %. Furthermore, as the base gas, various inert gases such as anitrogen (N₂) gas, an argon (Ar) gas and a helium (He) gas can be used.Especially, it is recommended to use a nitrogen (N₂) gas.

[0084] According to the aforementioned invention (26), the holdingtemperature is 100° C. or more and the holding time is 5 hours or more.The reasons are as follows. If the holding temperature is less than 100°C. or the holding time is less than 5 hours, the fluorination processinggas hardly diffuses into the heat exchanger or its component from thesurface thereof. Consequently, a good fluoride layer is not formed.Accordingly, it is preferable that the holding temperature is 100° C. ormore and the holding time is 5 hours or more. Especially, it is morepreferable that the holding temperature is 150° C. or more and theholding time is 10 hours or more. Although the upper limit of thepreferable holding time is not specifically limited, it is preferablethat it is 600° C. or less. On the other hand, although the upper limitof the preferable holding time is not specifically limited, it ispreferable that it is 50 hours or less. Furthermore, although theholding pressure is not specifically limited and can be set arbitrary,it is especially preferable that it falls within the range of from0.8×10⁵ to 1.5×10⁵ Pa.

[0085] According to the aforementioned invention (27), the fluoridelayer can be easily formed at the surface layer portion of the beatexchanger or its component. This fluorination processing can be easilyexecuted by, for example, an ion-implantation method using a known ionimplantation equipment. That is, fluorine is ionized with a filament ina decompressed atmosphere, and the fluorine ion is implanted into thepredetermined portion of the surface of the heat exchanger or itscomponent. By this, the fluoride layer is formed at the surface layerportion (including the surface) of the heat exchanger or its component.

[0086] According to the aforementioned invention (28), it becomespossible to obtain a heat exchanger excellent in corrosion resistance.

[0087] According to the aforementioned invention (25), it becomespossible to obtain a heat exchanger excellent in adhesion of the layercontaining catalyst (i.e., catalyst containing layer). Accordingly, thisheat exchanger is preferably used, especially, for a fuel cell. As thecatalyst, the aforementioned CO selective-oxidation reaction catalyst ofa fuel cell can be exemplified.

[0088] According to the aforementioned invention (30), it becomespossible to obtain a heat exchanger excellent in corrosion resistance.

[0089] According to the aforementioned invention (31), it becomespossible to obtain a beat exchanger excellent in adhesion of thecatalyst containing layer. Accordingly, this heat exchanger ispreferably used, especially, for a fuel cell. As the catalyst, theaforementioned CO selective-oxidation reaction catalyst of a fuel cellcan be exemplified.

[0090] According to the aforementioned invention (32), it becomespossible to obtain a heat exchanger excellent in corrosion resistance.In general, in cases where components are brazed with each other afterthe formation of fluoride layer at the surface layer portion of thecomponent, the fluoride layer may be damaged at the time of joiningHowever, according to the present invention, it becomes possible toprevent such a damage of the fluoride layer.

[0091] According to the aforementioned invention (33), it becomespossible to obtain a heat exchanger excellent in adhesion of thecatalyst containing layer. Furthermore, the damage of the catalystcontaining layer can be prevented. Accordingly, this heat exchanger ispreferably used, especially, for a fuel cell. As the catalyst, theaforementioned CO selective-oxidation reaction catalyst of a fuel cellcan be exemplified.

[0092] According to the aforementioned invention (34), it becomespossible to obtain a heat exchanger excellent in corrosion resistance.Furthermore, it becomes possible to prevent such a damage of thefluoride layer.

[0093] According to the aforementioned invention (35), it becomespossible to obtain a heat exchanger excellent in adhesion of thecatalyst containing layer. Furthermore, the damage of the catalystcontaining layer can be prevented. Accordingly, this heat exchanger ispreferably used, especially, for a fuel cell. As the catalyst, theaforementioned CO selective-oxidation reaction catalyst of a fuel cellcan be exemplified.

BRIEF DESCRIPTION OF TIM DRAWINGS

[0094]FIG. 1 is a perspective view showing an example of a tin-platetype heat exchanger to which the fluorination processing methodaccording to the present invention is applied.

[0095]FIG. 2 is a cross-sectional perspective view showing a principalportion for explaining the internal structure of the heat exchanger.

[0096]FIG. 3 is an enlarged cross-sectional view showing the heatexchanger component obtained in Example 1.

[0097]FIG. 4 is an enlarged cross-sectional view showing the heatexchanger component obtained in Example 2.

[0098]FIG. 5 is an enlarged cross-sectional view showing the heatexchanger component obtained in Example 3.

[0099]FIG. 6 is an enlarged cross-sectional view showing the heatexchanger component obtained in Example 4.

[0100]FIG. 7 is an enlarged cross-sectional view showing the heatexchanger component obtained in Example 6.

BEST MODE FOR CARRYING OUT THE PRESENT INVENTION

[0101] The present invention will be explained according to the attacheddrawings in order to detail the present invention.

[0102] In FIG. 1, the reference numeral “30” denotes a heat exchanger asan example to which the fluorination processing method according to thepresent invention is applied. This heat exchanger 30 is a fin-plate typeheat exchanger for a fuel cell which is used under a fuel gasenvironment of a fuel cell, and more specifically is used as amodification device of a fuel cell. In this figure, the referencenumeral “42” denotes a fuel gas of a fuel cell, and “43” denotes heatmedium. A hydrogen (H₂) gas is used as the aforementioned fuel gas 42. Arefrigerant is used as the aforementioned heat medium 43. For example, along-life coolant is used suitably.

[0103] As shown in FIGS. 1 and 2, this heat exchanger 30 is providedwith a plurality of plate-like tubes 34 each formed by coupling a pairof pan-like plates 33 and 33 in a face-to-face manner. The plate-liketubes 34 are stacked one on another with a corrugated outer fin 31intervened therebetween. Each of the plate-like tubes 34 is providedwith a flat heat medium passage 35 (refrigerant passage) therein asshown in FIG. 2. In this heat medium passage 35, a corrugated inner fin32, which is a member separated from the plate 33, is disposed.Furthermore, as shown in FIG. 1, at the end portions of the adjacentplates 33 of the adjacent plate-like tubes 34, short cylindrical tankportions 36 are formed. Both the tank portions 36 and 36 are engagedwith each other. Furthermore, at both sides of the plurality ofplate-like tubes 34 in the stack direction, side plates 37 and 37 forprotecting the outermost outer fins 31 are disposed. To one of the sideplates 37, a heat medium inlet pipe (refrigerant inlet pipe) 38 isconnected. To the other side plate 37, a heat medium outlet pipe(refrigerant outlet pipe) 39 is connected.

[0104] In this heat exchanger 30, the heat medium 43 is introduced intoone of the tank portion groups 36 via the heat medium inlet pipe 38. Andthen, as shown in FIG. 2, the introduced heat medium 43 passes throughthe heat medium passages 35 of the plurality of plate-like tubes 34 toreach the other tank portion groups 36. Thereafter, the heat medium isdischarged through the heat medium outlet pipe 39. On the other hand,the fuel gas 42 (i.e., hydrogen (H₂) gas) of a fuel cell passes throughthe gap 40 (hereinafter referred to as “fuel gas passage”) of theadjacent plate-like tubes 34 and 34 in which the outer fin 31 isdisposed. In this heat exchanger 30, heat exchange is performed betweenthe fuel gas 42 and the heat medium 43 when the fuel gas 42 passesthrough the fuel gas passage 40, thereby cooling the fuel gas 42.

[0105] This heat exchanger 30 is manufactured as follows. That is, theheat exchanger assembly shown in FIG. 1 is provisionally assembled byusing the outer fins 31, the inner fins 32, the plates 33 and the sideplates 37. Thereafter, this provisional assembly is held and tightenedusing stainless jigs (not shown) and bolts-and-nuts (riot shown). Then,in this assembled state, the aforementioned outer fins 31, the innerfins 32, the plates 33 and the side plates 37 are integrally brazed(i.e., vacuum brazed) in a vacuum heating furnace. Subsequently, theheat medium inlet pipe 38 and the heat medium outlet pipe 39 are joinedby welding to the side plates 37 and 37 of the assembly respectively.Thus, the aforementioned heat exchanger 30 is manufactured.

[0106] In the aforementioned heat exchanger 30, the outer fins 31, theinner fins 32, the plates 33 and the like correspond to the componentsof the heat exchanger 30.

[0107] The method of fluorination processing according to the presentinvention was applied to the aforementioned heat exchanger 30. Theexamples are shown as follows.

EXAMPLE 1

[0108] In order to manufacture the aforementioned heat exchanger 30, thefollowing outer fins 31, the inner fins 32 and the plates 33 wereprepared.

[0109] The outer fin 31 and the inner fin 32 were made of a barematerial (thickness: 0.1 mm) of aluminum alloy (material: JIS A3203),respectively. This bare material was the substrate of the outer fin 31and that of the inner fin 32, respectively.

[0110] The plate 33 was made of a clad material (thickness: 0.4 mm, skinmaterial clad rate: 15%) in which a skin material of aluminum alloy(material: JIS A4004) was clad on both surfaces of a core material ofaluminum alloy (material: JIS A3003). This clad material is the corematerial of the plate 33.

[0111] Thereafter, a heat exchanger assembly was provisionally assembledby using components including the outer fins 31, the inner tins 32 andthe plates 33, and thereafter the outer fins 31, the inner fins 32 andthe plates 33 were integrally secured while keeping the assembled state,whereby a predetermined heat exchanger assembly was manufactured. Thesecuring was performed by brazing (brazing temperature: about 600° C.)in a vacuum heating furnace.

[0112] Subsequently, the assembly was disposed in an atmospheric heatingfurnace, and a gas (a base gas: nitrogen (N₂) gas) containing a fluorine(F₂) gas as a fluorination processing gas was introduced in the furnace,whereby the gas in the furnace was replaced with the gas containing afluorine gas (F₂). The gas concentration of the fluorine in thefluorination processing gas was set to be 20 mass %. Subsequently, inthis fluorination processing gas atmosphere, the aforementioned assemblywas heated under the conditions of the holding temperature of 260° C.and the holding time of 24 hours (heating step). By this, both thesurfaces of the outer fin 31, those of the inner fin 32 and those of theplate 33 of the assembly were fluorinated, and a fluoride layer wasformed on each of the surfaces of these substrates. This fluoride layerwas substantially made of the structural elements of the substrate andfluorine. More concretely, the fluoride layer was substantially made ofan aluminum alloy fluoride such as aluminum fluoride

[0113] In the obtained heat exchanger, the thickness of the fluoridelayer of the outer fin 31 and that of the inner fin 32 were 0.3 μm,respectively, and the thickness of the fluoride layer of the plate 33was 0.1 μm. The thickness of the fluoride layer was obtained by a depthprofile measurement of the fluoride element with an XPS.

[0114]FIG. 3 is an enlarged cross-sectional view showing the component(i.e., the outer fin, the inner fin and the plate) of the heat exchanger33 obtained in Example 1. In this figure, the reference numeral “1” is asubstrate of the component, and “10” denotes a fluoride layer.

EXAMPLE 2

[0115] Outer fins 31, inner fins 32 and plates 33 which were similar tothose in Example 1 were prepared.

[0116] Thereafter, the outer fins 31, the inner fins 32 and the plates33 were used as components, and in the same method as in Example 1, abeat exchanger assembly in which the outer fins 31, the inner fins 32and the plates 33 were integrally brazed was made.

[0117] Thereafter, the assembly was immersed into 15% sulfuric-acidelectrolytic bath to thereby anodize both surfaces of the outer fin 31,those of the inner fin 32 and those of the plate 33 of the assembly.Thus, a sulfuric-acid anodized oxide layer (5 μm in thickness) as anintermediate layer was formed on the surface of these substrates.

[0118] Next, this assembly was heated in a fluorination processing gasatmosphere to fluorinate both surfaces of the outer fin 31, those of theinner fin 32 and those of the plate 33 of the assembly. Thus, a fluoridelayer was formed on the surface of the sulfuric-acid anodized oxidelayer of each of these substrates. In this case, the fluorinationprocessing conditions are the same as those of the aforementionedExample 1. This fluoride layer was substantially made of a compound ofthe structure elements of the sulfuric-acid anodized oxide layer andfluorine. More concretely, the fluoride layer was substantially made ofan aluminum alloy fluoride.

[0119] In the obtained heat exchanger, the fluoride layer of the outerfin 31 and that of the inner fin 32 were 0.3 μm in thickness,respectively, and the fluoride layer of the plate 33 was 0.1 μm inthickness.

[0120]FIG. 4 is an enlarged cross-sectional view showing the structuralmember of the heat exchanger obtained in Example 2. In this figure, thereference numeral “1” denotes a substrate of the structural member, “3”denotes an anodized oxide layer as an intermediate layer 2, and “10”denotes a fluoride layer.

EXAMPLE 3

[0121] Outer fins 31, inner fins 32 and plates 33 which were similar tothose in Example 1 were prepared.

[0122] Thereafter, the outer fins 31, the inner fins 32 and the plates33 were used as components, and in the same method as in Example 1, aheat exchanger assembly in which the outer fins 31, the inner fins 32and the plates 33 were integrally brazed was made.

[0123] Thereafter, both surfaces of the outer fin 31, those of the innerfin 32 and those of the plate 33 of the assembly were processed by aknown electroless plating method, whereby an electroless nickel platedlayer (5 μm in thickness) as an intermediate layer was formed on thesurface of each of the substrates. The concrete steps of the electrolessplating method employed here will be explained as follows. That is, theassembly was subjected to degreasing processing with a degreasing liquidof an alkali family, and then subjected to zincate processing (mainingredients: NaOH, ZnO) as pretreatment to thereby form a zinc layer onthe surface of the substrate. Subsequently, the assembly was immersed ina plating bath of 90° C. including sodium hypophosphite and nickelsulfate as main ingredients, which is commercially available chemicals,to cause reactions for a predetermined time. Thus, an electroless nickelplated layer was formed on the surface of the substrate.

[0124] Next, this assembly was heated in a fluorination processing gasatmosphere to fluorinate both surfaces of the outer fin 31, those of theinner fin 32 and those of the plate 33 of the assembly. Thus, a fluoridelayer was formed on the surface of the electroless nickel plated layerof each of these substrates. In this case, the fluorination processingconditions are the same as those of the aforementioned Example 1. Thisfluoride layer was substantially made of a compound of the structureelements of the electroless nickel plated layer and fluorine. Moreconcretely, the fluoride layer was substantially made of fluoride ofnickel such as nickel fluoride.

[0125] In the obtained heat exchanger, the fluoride layer of the outerfin 31 and that of the inner fin 32 were 4 μm in thickness,respectively, and the fluoride layer of the plate 33 was also 4 μm inthickness.

[0126]FIG. 5 is an enlarged cross-sectional view showing the structuralmember of the heat exchanger obtained in Example 3. In this figure, thereference numeral “1” denotes a substrate of the structural member, “4”denotes an electroless nickel plated layer as an intermediate layer 2,and “10” denotes a fluoride layer.

EXAMPLE 4

[0127] Outer fins 31, inner fins 32 and plates 33 which were similar tothose in Example 1 were prepared.

[0128] Thereafter, the outer fins 31, the inner fins 32 and the plates33 were used as components, and in the same method as in Example 1, aheat exchanger assembly in which the outer fins 31, the inner fins 32and the plates 33 were integrally brazed was made.

[0129] Thereafter, the assembly was immersed into 15% sulfuric-acidelectrolytic bath to thereby anodize both surfaces of the outer fin 31,those of the inner fin 32 and those of the plate 33 of the assembly.Thus, a sulfuric-acid anodized oxide layer (5 μm in thickness) as anintermediate layer was formed on the surface of these substrates.

[0130] Thereafter, both surfaces of the outer fin 31, those of the innerfin 32 and those of the plate 33 of the assembly were processed by aknown electroless plating method, whereby an electroless nickel platedlayer (5 μm in thickness) as an intermediate layer was formed on thesurface of each of the substrates. The concrete steps of the electrolessplating method employed here were the same as in the aforementionedExample 3.

[0131] Next, this assembly was heated in a fluorination processing gasatmosphere to fluorinate both surfaces of the outer fin 31, those of theinner fin 32 and those of the plate 33 of the assembly. Thus, a fluoridelayer was formed on the surface of the electroless nickel plated layerof each of these substrates. In this easer the fluorination processingconditions are the same as those of the aforementioned Example 1. Thisfluoride layer was substantially made of compounds of the structureelements of the electroless nickel plated layer and the fluorine. Moreconcretely, the fluoride layer was substantially made of fluoride ofnickel such as nickel fluoride.

[0132] In the obtained heat exchanger, the fluoride layer of the outerfin 31 and that of the inner fin 32 were 4 μm in thickness,respectively, and the fluoride layer of the plate 33 was also 4 μm inthickness.

[0133]FIG. 6 is an enlarged cross-sectional view showing the structuralmember of the heat exchanger obtained in Example 4. In this figure, thereference numeral “1” denotes a substrate of the structural member, “3”denotes an anodized oxide layer, “4” denotes an electroless nickelplated layer and “10” denotes a fluoride layer. In this Example 4, theintermediate layer 2 is composed of the anodized oxide layer 3 and theelectroless nickel plated layer 4.

[0134] <<Corrosion Resistant Tests>>

[0135] In order to evaluate the corrosion resistance of the heatexchangers of Examples 1 to 4, the following plate-like test pieces(dimension: 50×100 mm) were prepared.

[0136] <Test Pieces 1A and 1B>

[0137] The test piece 1A was a piece in which a substrate having thesame material and thickness as those of the outer fin and the inner finwas subjected to the same processing as in Example 1.

[0138] The test piece 1B was a piece in which a substrate having thesame material and thickness as those of the plate was subjected to thesame processing as in Example 1.

[0139] <Test pieces 2A and 2B>

[0140] The test piece 2A was a piece in which a substrate having thesame material and thickness as those of the outer fin and the inner finwas subjected to the same processing as in Example 2.

[0141] The test piece 2B was a piece in which a substrate having thesame material and thickness as those of the plate was subjected to thesame processing as in Example 2.

[0142] <Test Pieces 3A and 3B>

[0143] The test piece 3A was a piece in which a substrate having thesame material and thickness as those of the outer fin and the inner finwas subjected to the same processing as in Example 3.

[0144] The test piece 3B was a piece in which a substrate having thesame material and thickness as those of the plate was subjected to thesame processing as in Example 3.

[0145] <Test Pieces 4A and 4B>

[0146] The test piece 4A was a piece in which a substrate having thesame material as that of the outer fin and the inner fin was subjectedto the same processing as in Example 4.

[0147] The test piece 4B was a piece in which a substrate having thesame material and thickness as those of the plate was subjected to thesame processing as in Example 4.

[0148] <Test Pieces 5A and 5B>

[0149] The test piece SA was a piece in which only a sulfuric-acidanodized oxide layer was formed on a substrate having the same materialand thickness as those of the outer fin and the inner fin.

[0150] The test piece 5B was a piece in which only a sulfuric-acidanodized oxide layer was formed on a substrate having the same materialand thickness as those of the plate.

[0151] <Test Piece 6>

[0152] The test piece 6 was a piece in which no layer was formed on asubstrate of stainless steel (material: SUS304).

[0153] The aforementioned test pieces 1A to 6 were subjected to thefollowing corrosion test.

[0154] Each of the aforementioned test pieces 1A to 6 were subjected tothe test 150 times (cycles), wherein the test includes a step ofimmersing each test piece 1A to 6 in a corrosion water solution(ordinary temperature) of PH=1.3 containing hydrochloric acid, sulfuricacid, nitric acid, formic acid and acetic acid, a step of holding thetest piece taken out of the corrosion water solution for twenty minutesin a 200° C. high temperature furnace and a step of immersing the testpiece in the corrosion water solution again after cooling it toapproximately ordinary temperature. Thereafter, the decreased amount ofthe thickness and the decreased amount of weight due to the corrosion ofeach test piece was examined.

[0155] The results of the aforementioned corrosion test are shown inTable 1. Corrosion test Existence of (150 cycles) Fluorination ThicknessMaterial of processing decreased Overall Substrate Intermediate layerlayer amount (μm) evaluation Test piece 1A A3203 — Yes 0.4 ⊚ Test piece1B Clad — Yes 1.2 ⊚ material Test piece 2A A3203 Sulfuric-acid anodizedYes 3.2 ◯ oxide layer Test piece 2B Clad Sulfuric-acid anodized Yes 4.1◯ material oxide layer Test piece 3A A3203 Electroless nickel plated Yes1.3 ⊚ layer Test piece 3B Clad Electroless nickel plated Yes 1.1 ⊚material layer Test piece 4A A3203 Sulfuric-acid anodized Yes 1.3 ⊚oxide layer and Electroless nickel plated layer Test piece 4B CladSulfuric-acid anodized material oxide layer and Electroless Yes 1.1 ⊚nickel plated layer Test piece 5A A3203 Sulfuric-acid anodized No 9.1 Xoxide layer Test piece 5B Clad Sulfuric-acid anodized No 8.9 X materialoxide layer Test piece 6 Stainless — No 0.8 ⊚ steel

[0156] In the column of “Overall Evaluation” of the corrosion test inTable 1, “{circle over (∘)}” denotes “almost no corrosion,” “◯” denotes“slight corrosion,” and “×” denotes “heavy corrosion.”

[0157] According to the results of the corrosion tests shown in Table 1,it is confirmed that the test pieces 1A to 4B are excellent in corrosionresistance. Accordingly, it is confirmed that the heat exchangeraccording to Examples 1 to 4 are excellent in corrosion resistance.Especially, it is confirmed that the test pieces 1A, 1B, 3A, 3B, 4A and4B are extremely excellent in corrosion resistance. Accordingly, it isconfirmed that the heat exchanger according to Examples 1, 3 and 4 areextremely excellent in corrosion resistance.

[0158] Accordingly, the heat exchanger according to the presentinvention can be used for a long time period under a fuel cell gasenvironment in which a long time usage was used to be difficult.Furthermore, even under the water environment or vapor environment, itis possible to use the heat exchanger for a long time period.Furthermore, in cases where water is used as heat medium, the heatexchanger can be used for a long time period.

EXAMPLE 5

[0159] Outer fins 31, inner fins 32 and plates 33 which were similar tothose in Example 1 were prepared.

[0160] Thereafter, the outer fins 31, the inner fins 32 and the plates33 were used as components, and in the same method as in Example 1, aheat exchanger assembly in which the outer fins 31, the inner fins 32and the plates 33 were integrally brazed was made.

[0161] Subsequently, ionized fluorine was implanted on both surfaces ofthe outer fin 31, the outer fin side surface of the plate 33 (fluorineimplanting step). By this, a fluoride layer was formed on the surfacesof these substrates. The fluorination processing procedures by the ionimplantation method will be detailed as follows. That is, ionizedfluorine was implanted on the surfaces of the substrates by making thesubstrates negative in a fluorine gas (F₂) and performing a glowdischarge with the energy of 1 MeV. By this, the surfaces of thesubstrates were fluorinated

[0162] In the obtained heat exchanger, the fluoride layer of the outerfin 31 was 0.3 μm in thickness, and the fluoride layer of the plate 33was 0.1 μm in thickness.

EXAMPLE 6

[0163] Outer fins 31, inner fins 32 and plates 33 which were similar tothose in Example 1 were prepared.

[0164] Thereafter, the outer fins 31, the inner fins 32 and the plates33 were used as components, and in the same method as in Example 1, aheat exchanger assembly in which the outer fins 31, the inner fins 32and the plates 33 were integrally brazed was made.

[0165] Thereafter, both surfaces of the outer fin 31, those of the innerfin 32 and those of the plate 33 of the assembly were processed by aknown electroless plating method, whereby an electrolessnickel-phosphorus alloy plated layer (10 μm in thickness) as anintermediate layer was formed on the surface of each of the substrates.

[0166] Next, this assembly was healed in a fluorination processing gasatmosphere to fluorinate both surfaces of the outer fin 31, those of theinner fin 32 and those of the plate 33 of the assembly. Thus, a fluoridelayer was formed on the surface of the electroless nickel-phosphorusalloy plated layer of each of these substrates. In this case, thefluorination processing conditions are the same as those of theaforementioned Example 1. This fluoride layer was substantially made ofcompounds of the structure elements of the electroless nickel-phosphorusalloy plated layer and the fluorine. More concretely, the fluoride layerwas substantially made of a nickel-phosphorus alloy fluoride.

[0167] In the obtained heat exchanger, the fluoride layer of the outerfin 31 and that of the inner fin 32 were 0.3 μm in thickness, and thefluoride layer of the plate 33 was also 0.1 μm in thickness.

[0168] Next, on both surfaces of the outer fin 31 and the outer fin sidesurface of the plate 33 which were the portion to which a fuel gas(i.e., hydrogen (H₂) gas) of a fuel cell, a layer containing theaforementioned catalyst (thickness: 100 μm) was formed by applying andbaking CO selective-oxidation reaction catalyst thereto. The catalystwas used to promote the reaction of the carbon monoxide (CO) containedin the fuel gas of the fuel cell and oxygen (O₂).

[0169]FIG. 7 is an enlarged cross-sectional view showing the structuralmembers (outer fin, plate) of the heat exchanger obtained in Example 6.In this figure, the reference numeral “1” denotes a substrate of thestructural member, “4” denotes an electroless nickel-phosphorus alloyplated layer as an intermediate layer 2, and “10” denotes a fluoridelayer and “15” is a catalyst containing layer.

[0170] Next, in order to evaluate the corrosion resistance of the heatexchanger of Example 6, corrosion tests were performed under the sameconditions as in the aforementioned <<Corrosion resistance tests>>. As aresult, it is confirmed that this heat exchanger is extremely excellentin corrosion resistance.

[0171] Furthermore, in the heat exchanger of Example 6, the catalystcontaining layer 15 was formed on and firmly adhered to the surface ofthe fluoride layer 10. Accordingly, this reveals that the heat exchangercan be used for a long time period under a fuel gas environment of afuel cell.

[0172] Although some embodiments of the present invention are explained,the present invention is not limited to these embodiments and can bechanged in various manners.

[0173] For example, the inner fin 32 and the plate 33 may be integrallyformed.

[0174] Furthermore, in manufacturing a heat exchanger, structuralcomponents (outer fin, inner fin, plate, etc.) of the heat exchanger maybe heated in an atmosphere containing a fluorination processing gas(heating step) to form a fluoride layer on the surface layer portion ofthe structural components, and then the structural components may befixed to predetermined positions of the heat exchanger.

[0175] Furthermore, in manufacturing a heat exchanger, ionized fluorinemay be implanted on the surfaces of structural components (outer fin,inner fin, plate, etc.) of the heat exchanger (fluorine implanting step)to form a fluoride layer on the surface layer portion of the structuralcomponents, and then the structural components may be fixed topredetermined positions of the heat exchanger.

[0176] As mentioned above, the present invention will be summarized asfollows.

[0177] Since the heat exchanger according to the present inventionincludes heat exchanger structural components in which fluoride layer isformed on the surface layer portion, the heat exchanger is excellent incorrosion resistance as compared with prior heat exchangers, and can besuitably used as a heat exchanger using water as heat medium, especiallya heat exchanger using hot water or water containing long-life coolant.Furthermore, the heat exchanger can also be preferably used as a heatexchanger to be used under the conditions of water environment, vaporenvironment or fuel gas environment of a fuel cell.

[0178] According to the method of fluorinating a heat exchanger or itscomponents of the present invention, a fluoride layer can be easilyformed on the surface layer portion of the heat exchanger or itscomponents.

[0179] Furthermore, in cases where the concentration of the fluorine gasor that of the fluoride gas is set to fall within a predetermined range,it is possible to assuredly form a fluoride layer excellent in corrosionresistance on the surface layer portion of the heat exchanger or itscomponents.

[0180] According to the method of manufacturing a heat exchanger of thepresent invention, a heat exchanger excellent in corrosion resistancecan be obtained. The obtained heat exchanger can be suitably used as aheat exchanger using water as heat medium, especially a heat exchangerusing hot water or water containing long-life coolant. Furthermore, theheat exchanger can also be preferably used as a heat exchanger to beused under the conditions of water environment, vapor environment orfuel gas environment of a fuel cell.

INDUSTRIAL APPLICABILITY

[0181] The heat exchanger according to the present invention can bepreferably used for, for example, an evaporator, a condenser, aradiator, an oil cooler, especially for a heat exchanger for a fuelcell.

[0182] The method of fluorinating a beat exchanger or its components canbe preferably applied to a heat exchanger to be used as, for example, anevaporator, a condenser, a radiator, an oil cooler or its components,especially to a heat exchanger for a fuel cell or its components.

[0183] The method of manufacturing a heat exchanger can be preferablyapplied to a heat exchanger to be used as, for example, an evaporator, acondenser, a radiator, an oil cooler or its components, especially to aheat exchanger for a fuel cell.

[0184] The terms and descriptions in this specification are used onlyfor explanatory purposes and the present invention is not limited tothese, but many modifications and substitutions may be made withoutdeparting from the spirit of the scope of the present invention which isdefined by the appended claims.

What is claimed is:
 1. A heat exchanger including a heat exchangercomponent having a surface layer portion in which a fluoride layer isformed.
 2. The heat exchanger as recited in claim 1, wherein a thicknessof said fluoride layer falls within the range of from 2 nm to 10 μm. 3.The heat exchanger as recited in claim 1, wherein said heat exchanger isa fin-plate type heat exchanger, and wherein said component is at leastone of a fin and a plate.
 4. The heat exchanger as recited in claim 1,wherein said heat exchanger uses water as heat medium.
 5. The heatexchanger as recited in claim 1, wherein said beat exchanger is usedunder a water environment, a vapor environment, or a fuel gasenvironment of a fuel cell.
 6. The heat exchanger as recited in claim 1,wherein a layer containing catalyst is formed on a surface of saidfluoride layer.
 7. The heat exchanger as recited in claim 1, whereinsaid heat exchanger is for use in a fuel cell.
 8. The heat exchanger asrecited in claim 1, wherein said heat exchanger is a fin-plate type heatexchanger for a fuel tell to be used under a fuel gas environment of afuel cell, and wherein a layer containing catalyst for accelerating areaction of carbon monoxide contained in the fuel gas and oxygen.
 9. Theheat exchanger as recited in claim 1, wherein a substrate of saidcomponent is substantially made of aluminum or its alloy.
 10. The heatexchanger as recited in claim 1, wherein said fluoride layer is formedon a surface of a substrate of said component.
 11. The heat exchanger asrecited in claim 10, wherein said fluoride layer is substantially madeof fluoride generated by performing fluorination processing of saidsurface of said substrate.
 12. The heat exchanger as recited in claim 1,wherein said fluoride layer is formed on a surface of an intermediatelayer formed on a surface of a substrate of said component.
 13. The heatexchanger as recited in claim 12, wherein said fluoride layer issubstantially made of fluoride generated by performing fluorinationprocessing of said surface of said intermediate layer.
 14. The heatexchanger as recited in claim 12 or 13, wherein said intermediate layerincludes a layer which is substantially made of oxide generated byperforming forcible oxidation of said surface of said substrate.
 15. Theheat exchanger as recited in claim 12 or 13, wherein said intermediatelayer includes an anodized oxide layer formed by anodizing said surfaceof said substrate.
 16. The heat exchanger as recited in claim 1, whereinsaid fluoride layer is formed on a surface of an anodized oxide layerformed by anodizing a surface of a substrate of said component andsubstantially made of fluoride generated by performing fluorinationprocessing of said surface of said anodized oxide layer.
 17. The heatexchanger as recited in claim 1, wherein said fluoride layer is formedon a surface of a plated layer containing nickel formed on a surface ofa substrate of said component and substantially made of fluoridegenerated by performing fluorination processing of said surface of saidplated layer.
 18. The heat exchanger as recited in claim 17, whereinsaid plated layer is substantially made of electroless nickel plating.19. The heat exchanger as recited in claim 17, wherein said plated layeris substantially made of electroless nickel-phosphorus alloy platedlayer.
 20. The heat exchanger as recited in claim 1, wherein saidfluoride layer is formed on a surface of a plated layer constituting anintermediate layer including an anodized oxide layer formed by anodizinga surface of a substrate of said component and said plated layer formedon a surface of said anodized oxide layer and containing nickel, andsubstantially made of fluoride generated by performing fluorinationprocessing of said surface of said plated layer.
 21. The heat exchangeras recited in claim 20, wherein said plated layer is substantially madeof electroless nickel plating.
 22. The heal exchanger as recited inclaim 20, wherein said plated layer is substantially made of electrolessnickel-phosphorus alloy plating.
 23. A method of fluorinating a heatexchanger or its component, comprising: heating a heat exchanger or itscomponent in an atmosphere containing a fluorination processing gas tothereby form a fluoride layer in a surface layer portion of said heatexchanger or its component.
 24. The method of fluorinating a heatexchanger or its component as recited in claim 23, wherein saidfluorination processing gas is at least one gas selected from the groupconsisting of a fluorine gas, a chlorine trifluoride gas and a nitrogenfluoride gas, wherein an inert gas is used as a base gas of saidatmosphere, and wherein concentration of said fluorine gas or that ofsaid fluoride gas is set so as to fall within the range of from 5 to 80mass %.
 25. The method of fluorinating a heat exchanger or its componentas recited in claim 24, wherein said concentration of said fluorine gasor that of said fluoride gas is set so as to fall within the range offrom 10 to 60 mass %.
 26. The method of fluorinating a heat exchanger orits component as recited in claim 23, wherein said heating is performedunder a heat processing condition that a holding temperature is 100° C.or more and a holding time is 5 hours or more.
 27. A method offluorinating a heat exchanger or its component, comprising: implantingan ionized fluorine into at least a part of a surface of a heatexchanger or its component to thereby form a fluoride layer on a surfacelayer portion of said heat exchanger or its component.
 28. A method ofmanufacturing a heat exchanger, comprising: a heating step for heating aheat exchanger component in an atmosphere containing a fluorinationprocessing gas; and a fixing step for fixing said component processed bysaid heating step to a predetermined position of a desired heatexchanger.
 29. The method of manufacturing a heat exchanger as recitedin claim 28, further comprising a catalyst containing layer forming stepfor forming a layer containing catalyst on a surface of said componentprocessed by said heating step.
 30. A method of manufacturing a heatexchanger, comprising: a fluorine implanting step for implanting anionized fluorine into at least a part of a surface of a heat exchangercomponent; and a fixing step for fixing said component processed by saidfluorine implanting step to a predetermined position of a desired heatexchanger.
 31. The method of manufacturing a heat exchanger according toclaim 30, further comprising a catalyst containing layer forming stepfor forming a layer containing catalyst on a portion of said surface ofsaid component processed by said fluorine implanting stop to which saidfluorine is implanted.
 32. A method of manufacturing a heat exchanger,comprising: a heating step for heating a heat exchanger assembly in anatmosphere containing a fluorination processing gas, wherein said heatexchanger assembly is formed by assembling a plurality of heat exchangercomponents and integrally brazing said plurality of heat exchangercomponents in an assembled state.
 33. The method of manufacturing a heatexchanger as recited in claim 32, further comprising a catalystcontaining layer forming step for forming a layer containing catalyst ona surface of said assembly processed by said heating step.
 34. A methodof manufacturing a heat exchanger, comprising: a fluorine implantingstep for implanting an ionized fluorine into at least a part of asurface of a heat exchanger assembly, wherein said heat exchangerassembly is formed by assembling a plurality of heat exchangercomponents and integrally brazing said plurality of heat exchangercomponents in an assembled state.
 35. The method of manufacturing a heatexchanger as recited in claim 34, further comprising a catalystcontaining layer forming step for forming a layer containing catalyst ona portion of said surface of said assembly processed by said fluorineimplanting step to which said fluorine is implanted.